Isocoumarins 1-indenones

In a total synthesis of coriandrin 68, the isocoumarin unit is generated by the thermal rearrangement of an indenone epoxide 67, the first application of a cycloreversion route to isocoumarin synthesis (Scheme 46) <00TL3677>. 

An epoxide is an intermediate in the conversion of indenones into isocoumarins brought about by hydrogen peroxide (43JA1230, 63JA3529). 

Flash vacuum pyrolysis (FVP) of the indenone epoxides 795 results in a thermal rearrangement to form the intermediate ketene, which can undergo electrocyclization to afford isocoumarins in high yield (Scheme 221) <2000TL3677>. 

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